An example of a prior art connector is described in document WO 95/33157.
That document describes a body with two circumferential recesses which house two sealing elements having an arched shape in the zone in contact with the inner surface of the hose. The ratio of the size of the recesses and of the sealing element, together with the geometry of the sealing element, guarantees that a seal is maintained.
It should be noticed that in the connector described in document WO95/33157, the high level of interference present between the hose and the connector requires a special widening tool to allow fitting of the connector in the hose.
This is due to the fact that the body is equipped with ramp-like elements which are also designed to prevent the connector from coming off the hose.
However, it should be noticed that such ramp-like elements may cause tears on the inner part of the hose.
But such a connector does not allow lasting performance, due to the relatively large dimensions of the contact surface between the hose and the sealing element.
Another example of a prior art connector is described in document WO 00/19137.
Document WO 00/19137 describes a connector in which the positioning and holding in place of O-ring type sealing elements is guaranteed by the size of the recess.
In that connector the O-ring cross-section centre point is positioned below the edge of the recess.
Outside the hose, at each sealing element, there is a metal clip, clamped to a predetermined diameter, thus applying a pressure between the inner surface of the hose and the sealing element, sufficient to guarantee a correct seal for the assembly.
Application of the pressure needed to guarantee the connector seal can be carried out using crimped rings or reusable systems.
One problem with the connector described above is due to the fact that the shape of the connector at the recesses for housing the O-ring sealing elements, with a circular cross-section, does not guarantee that such sealing elements remain in position during fitting of the hose, particularly where lubricants are not used. In fact, the hose drags the O-ring axially along the connector, imparting a rotary movement and forcing it out of its seat, even if the depth of the seat is greater than the radius of the O-ring.
It should be noticed that the chain of dimensional tolerances of the assembly made up of the connector, the O-ring and the hose, together with the variability of the mechanical features of the elastomers used, may create the disadvantage of forcing the O-ring out of the recess and dragging it on the cylindrical element by means of a rolling phenomenon.
That disadvantage causes delays and various problems in operations for assembling the hose-connector system and, in the worst cases, may result in a connector malfunction.
Document EP 1933073 describes a connector which has a profile with a plurality of ramps and a seat interposed between two ramps in which an O-ring is inserted.
The seat for the sealing element is shaped with a bottom wall and two lateral walls at right angles to it. The sealing element is inserted in the seat with axial play.
This type of connector has the same disadvantage as previously encountered, that is to say, the O-ring is forced out of the seat during the assembly step.
Connectors substantially similar to the previous one in EP 1933073 are described in documents DE202008006797, EP 1882876 and WO03/064912. Even for those types of connectors there is the disadvantage of the O-ring being forced out of the seat during the assembly step.